This invention relates to piston and cylinder assemblies and further to a piston and seal assembly for use with a piston and cylinder assembly. More particularly, this invention relates to a piston and cylinder assembly in which the cylinder defines an annular pressure chamber and in which the piston is annular and is slidably received in the annular pressure chamber.
Annular piston and cylinder assemblies are in wide use in industry. For example, such assemblies are utilized in vehicular clutch assemblies wherein the assembly is positioned concentrically around the main drive shaft of the vehicle and the annular piston is connected to the release bearing of the clutch assembly so that sliding movement of the annular piston in the annular pressure chamber of the cylinder operates in known manner to engage and disengage the clutch of the vehicle. It is important in assemblies of this type that the pressure chamber defined within the cylinder be effectively and adequately sealed. In one prior art sealing arrangement, a separate annular elastomeric seal is positioned in the pressure chamber for axial movement with the piston. Whereas this arrangement has been generally satisfactory, there are operating environments in which the separate seal becomes twisted in the pressure chamber and fails to provide an effective sealing action. In another prior art sealing arrangement, the annular seal is secured to the inboard annular edge of the piston. In this prior art arrangement, whereas the seal is essentially precluded from twisting in the pressure chamber, the seal has a tendency to extrude itself relative to the associated piston and thereby derogate the sealing action and/or derogate the travel efficiency of the assembly. The attached seal also can become detached from the associated piston with consequent loss of an effective sealing operation.